The present invention generally relates to MEMS-based tile assemblies and methods of fabricating same, and more particularly, to MEMS-based tile assemblies wherein vertical alignment of and electrical interconnection of MEMS tiles is achieved using metallized elastic spheres and precision pyramid shaped pits etched on the surface of silicon substrates. Such MEMS-based tile assemblies may be used to produce large area, multi-tile (substrate), transmit/receive subsystems for use in large area micro-machined phased arrays.
Alignment registration between vertically stacked, conventional high thermal conductivity substrates such as aluminum nitride or beryllium oxide with vertical vias is limited by the accuracy and repeatability of via hole fabrication processes. Replacement of high thermal conductivity, ceramic based substrates with high resistivity, single crystal silicon will allow the fabrication of large area tile array systems, because precision, micron-accuracy, vertical vias can be fabricated with microelectronics based MEMS techniques. Furthermore, large size, precision, flat, silicon wafers and high volume manufacturing techniques are readily available. Replacement of the traditional face-up MMIC/aluminum nitride tile assembly with flip-chip/MEMS based technology will lead to a 3-to-5 fold in subarray cost reduction, enabling fabrication of large area sub-arrays containing on the order of 100 transceiver elements.
Aluminum nitride is the favored dielectric substrate material for high power active radar tile subarray because of its high thermal conductivity and its nontoxic property. However, precision circuitry with vertical via cannot be batch fabricated using conventional techniques because of shrinkage associated with firing the ceramic material. Consequently, via holes must be individually drilled. Maintaining precision aligrnment registration of the vertical via electrical connections from tile to tile is the cost driver of microwave subarray assemblies. Availability of large area, aluminum nitride substrate with built-in multilayer interconnect circuitry and precision vertical via limits the maximum number of transceiver element contained in a subarray.
Accordingly, it is an objective of the present invention to provide for MEMS based tile assemblies and methods of fabricating such tile assemblies. It is a further objective of the present invention to provide for MEMS based tile assemblies and methods of fabricating such tile assemblies that may be used to produce large area, multi-tile (substrate), transmit/receive subsystems for use in large area micro-machined phased arrays.